Such a display arrangement is described in U.S. Pat. No. 6,023,372 and is shown in plan view in FIG. 1.
Such an arrangement 10 comprises a housing assembly 16 comprising a first housing 20 containing a circuit for receiving data or images and containing an image-generator assembly. The light transmitted by the image-generator assembly is relayed via an optical device 14 to the eye of the user, e.g. through a lens 24 of a pair of spectacles. This light pipe 14 comprises a transparent rectilinear optical relay 26 transmitting light along its longitudinal axis A-A′, and a deflector assembly 28 comprising a mirror 30 disposed on a surface that is inclined relative to the first axis A-A′ and an aspherical lens 32 disposed in register with the inclined wall and having an axis of revolution B-B′ which, in this example, is perpendicular to the first axis A-A′. The housing assembly 16 is mounted on one of the temples 34 of a frame for a pair of spectacles by a fastener arrangement 36.
The pipe presents a given maximum height Hmax outside the thickness of the lens, and a given mean length Lmoy along its longitudinal axis A-A′. By way of example, such a prior art light pipe presents a maximum height Hmax of 11 millimeters (mm) and a mean length Lmoy of 32 mm. With such a prior art arrangement, it is possible to obtain an image as seen by the user that has an apparent angular size of 11.5°.
The pipe is advantageously made of thermoplastic material.